The present invention relates to a mixing chamber for a molding system, and more particularly to a longitudinal mixer which minimizes the requirement of flushing.
A typical molding system provides for the mixing of at least two fluid materials to form a settable mixture which is discharged into a mold cavity to form a finished article. One particular mixture includes three fluid material components which form a matrix having a catalyst, a matrix polymer and a foaming agent. The fluid materials are typically fed from a supply by a delivery or feed assembly which communicates with a mixing head. The fluid materials are mixed by the mixing head and discharged into the mold cavity to form the molded article.
Once mixed in the mix head the fluid material components gels and then becomes hard in a relatively timely fashion. It is therefore essential to cleanse the mixing head of any residual material to prevent the remnants from hardening within. Typically, the mix head is flushed after each cycle to remove the remnants and prepare the mix head for the next injection cycle. This is time consuming and expensive as the flushing fluid must be safely disposed of after usage.
Accordingly, it is desirable to provide a mix head which minimizes the necessity of flushing between injection cycles to decrease the cycle time for production and expense of each finished article.
The present invention provides a mix head assembly including a substantially tubular mix chamber. A mixer is rotatably mounted within the mix chamber which defines an axis. The mixer extends for a longitudinal length along the axis and defines a multiple of vanes which extend substantially perpendicular to the axis. Each of the vanes includes a plurality of steps which agitate the fluid material components as the mixer is rotated.
A plunger is movably mounted in the mix chamber for movement along the axis. The plunger defines an outer diameter which closely fits within the mix chamber and an inner configuration which closely fits over the mixer. As the plunger is driven along the axis, the plunger cleans any fluid material remnants from the mixer. That is, the plunger scrapes the fluid material off the mixer such that no remnants remain within the mix chamber. The necessity of flushing between injection cycles is therefore eliminated as the plunger need only be cycled up and down. Cycle time for production and expense of each finished article is thereby decreased.
The present invention therefore provides a mix head which minimizes the necessity of flushing between injection cycles to decrease the cycle time for production and expense of each finished article.